I do think the default a long time ago used to be very low. I know I went in at account creation and set it to something way higher than it's default at the time.
Looking now though, it says 100100 for me. But i also know i changed my master password at some point, so maybe i got reset to the current default.
According to [1], there were 5,000 client-side rounds of SHA256 in key derivation in June 2015.
It does sound like a missed opportunity to have an at-login upgrade mechanism to upgrade KDF rounds that can be carried out seamlessly or near-seamlessly during the login process. Or at least actively nudging users to change password and thus raise their KDF rounds that way through the default.
One would think that the UI where one routinely enters their master password could silently double as a start using the new default UI, as the change-password UI seemingly does.
Looking now though, it says 100100 for me. But i also know i changed my master password at some point, so maybe i got reset to the current default.